Research was conducted to determine the role of uptake, distribution, and metabolism of quinclorac in differential sensitivity of southern crabgrass and Kentucky bluegrass. At 0.5 h, quinclorac uptake was 85% in southern crabgrass and 66% in bluegrass. Uptake and distribution differed between species. By 128 h, Kentucky bluegrass had uniformly distributed quinclorac and exuded 17% into the nutrient solution. Metabolism of quinclorac was limited to less than 3.6% of the applied 14C in the two species, at 128 h. Selectivity of quinclorac may be influenced by differences in uptake, distribution, and exudation by the roots but not by metabolism.